Step 1. Go to tests
Click the menu icon 
on the top left of your screen and click Tests in the main menu.
Step 2. Create a top-level group
To create a new top-level group, click the plus icon 
in the Groups index.
Step 3. Name the group
Enter a name for the group and click Save.
Step 4. Create a sub-group
The group you created appears in the index. Point to the group's 3-dot icon 
and choose Create to create a sub-group in side the group you just created.
Step 5. Name the sub-group
Enter a name for the sub-group and click Save. Now your group has a sub-group. Click the expand
icon beside the top-level group in the index to see its sub-groups.
You can only create one level of sub-groups to keep it easy to browse and manage tests.